Introductory. Structure and properties of simple liquids and solutions: a review

The structure of a simple liquid is determined primarily by the repulsive forces between the molecules. The effects of the attractive forces can be found by perturbation treatments, of which that of van der Waals is the prototype, and that of Barker and Henderson the most recent. The repulsive forces are equally important in determining the structures of mixtures of spherical molecules of different sizes—structures which are quite different from those found in the unmixed liquids. Recent Monte Carlo calculations by Singer can be used as a standard by which theories of mixtures can be judged, and it is shown that the only adequate theories are those which do justice to this difference in structures. It is suggested that the shape of molecules is often of less importance than their size in determining the free energy, and hence that theories of solutions of n-alkanes or of linear polymers do not, in their results, differ greatly from those of mixtures of spherical molecules of different sizes.